PWR Supply

Discussion in 'General Electronics Chat' started by trickyrick, Sep 18, 2013.

  1. trickyrick

    Thread Starter New Member

    Sep 18, 2013
    Hi guys
    I have a laptop power supply to an HP Laptop that my Daughter had some time ago my Daughter removed the ground prong on the plug. The other day I plugged it in but reversed the plug heard a pop and now my computer will not run on the Battery only AC (not sure if its the motherboard or the circuit in the battery thats fried)
    My question is Y did that happen.
    If I had a 12 volt power supply and then a bridge rectifier with my volt meter on the secondary side measuring the DC would I see the polarity change when I reversed the wires on the primary side (110)
    Thanks Rick
    PS any idea if I will now have to chance the motherboard or just purchase a new battery for the laptop
  2. PackratKing

    Well-Known Member

    Jul 13, 2008
    Protocol says that there *should* be reverse-polarity protection on the DC feed, I'm not so sure that applies to AC.

    You may have shot yourself in the to speak... can you post a shot of the setup, I'm not clear about whether it was an AC adapter that popped, or something in the battery itself as you said...... you would have to mutilate the battery itself, to open it to look for damage, ... I'll bet it damaged something in the adapter brick
  3. trickyrick

    Thread Starter New Member

    Sep 18, 2013
    Thanks for the reply
    Its not the pwr supply. It still works so its either the battery or the MB. But Im still not sure why that happened. If you take any DC pwr supply does the polarity change if you were to reverse the wires on the AC side.
  4. shortbus

    AAC Fanatic!

    Sep 30, 2009
    The short answer is, no. a diode bridge doesn't care what side of the AC is hooked to it.

    If the laptop still works on AC, the MB probably isn't the problem.
    PackratKing likes this.
  5. wayneh


    Sep 9, 2010
    You may be right but the motherboard does hold power MOSFETs that could have blown, that could prevent battery operation. So the OP may not be completely out of the woods. It's better than running only off the battery though. Been there.

    The simple way to test is to get another similar laptop so you can test the laptop, adapter and battery versus known-good ones. craigslist is your friend.
    PackratKing likes this.
  6. trickyrick

    Thread Starter New Member

    Sep 18, 2013
    I am assuming that its the battery on the outside contacts of the battery I measure 0 volts I took the battery apart and I can measure 4 volts accross the 6 cells so I think I buggered the battery circuit.
    Now for my 1 question. When I reversed the AC on the DC power supply why did it damage the circuit in the Battery. The polarity would not have changed.
  7. BillB3857

    Senior Member

    Feb 28, 2009
    Did you have the laptop connected to any external devices when this happened?
  8. trickyrick

    Thread Starter New Member

    Sep 18, 2013
    No nothing